The present invention generally relates to a socket wrench and, more particularly, toward a socket wrench assembly that accurately threads a nut a predetermined amount or distance on a threaded shaft.
Devices for positioning a nut a predetermined depth on a threaded shaft or bolt are known in the art. One known device utilizes a spring to place a nut at a particular depth on a threaded shaft. This prior art device includes a commercially available socket, a pin, and a spring. The socket is cylindrical in shape, with an inner and outer diameter, is open at the top end, and is substantially closed at the bottom end. The socket has a longitudinal axis, with a length extending from the bottom to the top of the socket.
The pin is cylindrical in shape, with a smaller diameter than the inside diameter of the socket and a distal end disposed beneath the open end of the socket. The spring is wrapped around the pin, so that the pin fits inside the spring. The spring has a common longitudinal axis with the socket and the pin, so that it extends from the bottom of the socket toward the top of the socket. The length of the spring is shorter than the length of the pin.
The pin fits inside the center of a nut, and extends partially through the nut. The nut is registered in the open end of the socket and rests on the top of the spring, so that the spring keeps the nut from falling toward the bottom of the socket. The nut is turned onto the threaded shaft by rotation of the socket, with the depth or amount the nut is threaded onto the shaft being limited by engagement of the pin""s distal end with the end of the shaft.
Another prior art device, shown in FIG. 1, includes a socket 10, a brass sleeve 12 and a pin 14. The socket 10 is similar to the socket described above, and the pin 14 is also similar to the pin described above. However, in this design the brass sleeve 12 is used instead of a spring. The brass sleeve 12 is cylindrical, with a longitudinal axis that is common with the longitudinal axis of the pin 14 and the socket 10. An inner diameter of the sleeve 12 is slightly larger than the outer diameter of the pin 14, so that the pin can be inserted into the sleeve 12. The brass sleeve 12 has an outer surface that is shaped to be closely received in the socket 10, so that the sleeve has an interference fit inside the socket. The brass sleeve 12 has a length that extends from the bottom of the socket 10 toward the top of the socket, and is shorter than the length of the pin 14. When the pin is positioned inside a portion of a nut, the nut rests on the top of the brass sleeve. The sleeve prevents the nut from falling to the bottom of the socket.
Unfortunately, the prior art devices suffer from disadvantages that limit their effectiveness in production or manufacturing applications. For example, in the spring loaded device, the spring wears out over time, which makes initial threaded engagement of the nut with the bolt problematic. Therefore, the spring-biased device requires periodic replacement of the spring.
In the other prior art device illustrated in FIG. 1, the brass sleeve gradually wears, which also eventually presents problems in registering the nut on the threaded shaft. More specifically, when the brass sleeve wears, the pin extends farther through the nut and causes the shaft to engage the pin before the nut is threaded on the shaft the desired predetermined distance. In extreme cases, the pin will extend so far through the nut that the nut cannot be threaded onto the shaft. Also, the pin is not positively held in place and, due to the challenging environment presented in manufacturing situations, is moved longitudinally within the sleeve. Such movement also causes premature engagement between the pin and shaft, and thus causes the nut to be imprecisely threaded onto the shaft. In extreme cases, this movement of the pin prevents the nut from threadably engaging the shaft. It has been found that, in manufacturing situations, repair or replacement of the aforementioned nut positioning tool must be performed about every two weeks in order to maintain acceptable quality. As can be appreciated, this frequency of replacement is undesirable for a basic manufacturing tool.
Therefore, there is a need in the art for a device that precisely and reliably positions a nut on a threaded shaft. Moreover, there exists a need in the art for a device that is durable and can be used for extended periods of time without repair or replacement.
The present invention is directed toward a device and method for precisely and reliably positioning a nut on a threaded shaft. The present invention provides an assembly including a socket and an insert member. The insert member is cylindrical, has a longitudinal axis common to the socket, and extends from the bottom of the socket toward the top of the socket. The insert member has a body portion with an outer surface that corresponds to an inner surface of the socket, so that the insert member has an interference fit with the socket and rotates with the socket. The one-piece insert shows improved wear and can be used for extended periods of time without repair or replacement. Moreover, the one-piece insert provides for more accurate nut placement on a threaded shaft because the top of the insert member, which includes a surface adapted to support the nut and a surface that serves to engage the shaft upon which the nut is threaded, is maintained at a constant distance from the top of the socket.